The present invention relates to a rotary and up-down mechanism of an industrial robot, and more particularly to a rotary and up-down mechanism which attains highly precise positioning accuracy.
In the conventional type mechanism, a double bearing mechanism having a rotary and linear movement is employed. For example as shown in FIG. 1, a rotary outer tubular part 5 is rotated by a motor 2 mounted on a base 1, and an inner tubular part 12 integrally rotated by the outer part 5 is driven in an up-down mode by a motor 7. Namely, a gear wheel 3 of a motor shaft 4 is geared to a gear wheel 5a of the outer part 5 the part 5 being rotatably supported on the base 1 through a bearing portion 6 and connected to rotate the inner tubular part 12 by a pin 13 mounted to a nut 14.
Further, the inner part 12 is driven in an up-down mode by a feed nut 10 guided in the up-down mode according to a stationary rod 11 by a motor shaft 8 and a feed screw 9. By this construction, the inner part 12 can undergo linear sliding movement inside the outer part 5 through a bearing portion 18. The inner part 12 is integrally mounted with a frame 15 by a bolt 16 and is able to drive an arm 17 in rotary and up-down modes.
However, in the above noted conventional type, the positioning accuracy of the arm 17 driven by the frame 15 is not so good since the frame position is dependent on a rotary bearing 6 and linear bearing 18 and to improve the working accuracy requires use of expensive bearings.
Further, the bearing construction is composed of double construction whereby a shape becomes very complicated, a moment load and axial load are applied to an outer bearing portion, and therefore, the whole shape becomes larger and it is necessary to provide a large driving power.
The present invention aims to eliminate the above noted difficulty and insufficiency, and it is an object to provide a small and simple rotary and up-down mechanism for a robot having a high positioning accuracy of the frame by a part integrally formed with the frame and supported in a rotatable and linearly movable manner.